Conventional electrical connection devices generally adopt a direct insertion manner, for example, using common two-hole or three-hole sockets and corresponding plugs. Power is on when a plug is inserted into a socket, while power is off when the plug is pulled out of the socket. This conventional electrical connection manner is convenient in use. However, the electrical connection in this manner completely depends on contact between metal contacts that press against each other, as well as conductivity of the metal contacts. The metal contacts need to have both a conductive function and a fastening function. In an actual application, a loose connection or a bad connection usually occurs, resulting in poor reliability of an electrical connection. Moreover, such an electrical connection manner easily causes an electric spark during insertion or pullout of the plug, and even incurs an electrical accident in a serious case. In addition, metal contacts of a conventional plug expose relatively long, which not only wastes materials, but also causes safety threats such as an electric shock; besides, the relatively long metal contacts are easily bent during conveyance, which affects the normal use.
To eliminate the foregoing defects of unsafe and unreliable electrical connection between the conventional straight insertion type plugs and sockets, some novel plugs and sockets emerge in the market, which also change the existing electrical connection manner. Especially for rotary plugs and sockets, generally, a circular plug having metal contacts on its outer wall is inserted into a socket with a circular hole, and is rotated by 90° to enable connection between the contacts of the plug and the socket. There are generally two situations when the plug is pulled out of the socket. In a first situation, the plug is rotated counterclockwise to pop out of the socket. However, such a pullout manner has a low power-off speed and results in certain safety threats in the case of an emergency. In a second situation, the plug can be pulled out directly. This manner ensures electrical safety. However, most users exert a small force when trying to directly pull out the plug, and may easily have a feeling that the plug cannot be directly pulled out. As a result, the users still adopt the counterclockwise rotation manner to cut off the power. Moreover, this manner of directly pulling out the plug requires a large force, which may cause large damages to the plug and the socket and affect their service life. Besides, the following situation usually occurs during use of such a rotary socket: when one user inserts a plug into a socket, another user may not know that this socket is a rotary socket and has difficulty in cutting off the power. In addition, the rotary socket has a defect that the plug is easily rotated counterclockwise in use under a tiny external force, and as a result, the metal contacts have poor contact stability and an unexpected power outage easily occurs. Therefore, the users often feel that it is inconvenient to use the rotary plugs, and thus such plugs and sockets are received unfavorably in the market.
With reference to advantages of the conventional straight insertion type plugs and sockets and advantages of the rotary plugs and sockets, novel straight insertion type plugs and sockets emerge in the market, which have structures similar to those of the rotary plugs and sockets and enable direct insertion and pullout. However, for such a plug and a socket, a single-side locking slot and a locking plate are used to fasten the plug, and a locking device is needed to work in cooperation to implement locking or unlocking, so that the operation is still rather complicated. In addition, under a single-side force from the locking device, a gap easily occurs between contacts of the plug and the socket, resulting in poor stability of the electrical connection and severe heat emission of the contacts.